vlan: introduce *vlan_hwaccel_push_inside helpers

Use them to push skb->vlan_tci into the payload and avoid code
duplication.

Signed-off-by: Jiri Pirko <jiri@resnulli.us>
Acked-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index c63e60e..f37ca3e 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -425,12 +425,10 @@
 		if (!nskb)
 			return -ENOMEM;
 
-		nskb = vlan_insert_tag_set_proto(nskb, nskb->vlan_proto,
-						 vlan_tx_tag_get(nskb));
+		nskb = __vlan_hwaccel_push_inside(nskb);
 		if (!nskb)
 			return -ENOMEM;
 
-		nskb->vlan_tci = 0;
 		skb = nskb;
 	}